We hear a lot about endangered or threatened species. But what exactly is an endangered species? What does it mean when a species is threatened?

An endangered species is one that is at risk (in danger) of extinction. The formal criterion is that the species is included on one or more official lists, such as the IUCN Red List, the CITES Appendix, or the USA-ESA Endangered Species list. Generally, species most at risk (i.e., endangered) are included on all three lists. Species on the lists can change in status. Most move from less to more serious, such as from Vulnerable to Endangered. However, some species whose populations are recovering can be delisted. It's also possible for a previously declared extinct species to be rediscovered, such as the ivory-billed woodpecker (Campephilus principalis), which was found in the United States in 2005 after being declared extinct by the IUCN in 1996. Categories less serious than Endangered are recognized, depending on the organization. In the tables below, you can see the summary definition for each of the three organizations, and how each of these compare.

The CITES list is intended to help control trade in endangered species. Species in CITES Appendices may be at risk of extinction or at least of concern. Thus a species that is IUCN Endangered or Vulnerable will likely be covered by CITES but a species that is near threatened may not be. The Conference of the Parties (CoP) is the supreme decision-making body of the Convention. It comprises member States, and has agreed on biological and trade criteria to help determine whether a species should be included in Appendices I or II. At each regular meeting of the CoP, proposals based on those criteria to amend these two Appendices are reviewed. Amendment proposals are discussed and then voted upon. Changes to Appendix III follow a different procedure from changes to Appendices I and II, as each country is entitled to make unilateral amendments to it.

The Endangered Species Act is a program to ensure conservation of threatened and endangered plants and animals and their habitats. The U.S. Fish and Wildlife Service (FWS) of the Department of the Interior maintains the list of 632 endangered species (326 are plants) and 190 threatened species (78 are plants).

Species include birds, insects, fish, reptiles, mammals, crustaceans, flowers, grasses and trees. Anyone can petition FWS to include a species on this list. The law prohibits any action (administrative or real) that results in a "taking" of a listed species, or adversely affects habitat. Likewise, import, export, interstate, and foreign commerce of listed species are all prohibited.

EPA's decision to register a pesticide is based in part on the risk of adverse effects on endangered species as well as environmental fate (how a pesticide will affect habitat). Under FIFRA, EPA can issue emergency suspensions of certain pesticides to cancel or restrict their use if an endangered species will be adversely affected. Under a new program, EPA, FWS, and USDA are distributing hundreds of county bulletins that include habitat maps, pesticide use elimitations, and other actions required to protect listed species.

Congress enacted the Endangered Species Act to identify species of fish, wildlife, and plants that are of aesthetic, ecological, educational, historical, recreational, and scientific value to the U.S. government and its people. The reason we have the Endangered Species Act is to provide a way to save endangered species and their environments. The Act is intended to do more than just list species as endangered or threatened, but also to restore the populations of these species to where they can be taken off the list.

In the 1960's many environmental laws were passed, but it wasn't until 1973, when congress passed the Endangered Species Act, that important protection was granted to rare species. The Endangered Species Act empowers the Secretary of the Interior to determine if a species is threatened or endangered, based on man-made factors that impact their continued existence. Many consider the Endangered Species Act as the most important environmental law ever passed.

USA-ESA Definitions

• Endangered: If a species is listed as endangered, it is in danger of extinction throughout all or a portion of their range.
• Threatened: If a species is listed as threatened, such as the sea otters, it is likely to become endangered in the near future.
• Candidates: Used to describe plant, fish or animal species that may become endangered or threatened. The Fish and Wildlife Service keeps a list of candidate species.

Wikipedia: Endangered species
World Wildlife Fund: Endangered Species
WildAid: Endangered Species Overview
Animal Info: Information on Endangered Mammals
eelink.net: Endangered Species
BlinkBits: Endangered Species Bio, Pictures, News and RSS Feeds
National Wildlife Federation: Protecting Wildlife
Marinebio.org: Threatened and Endangered Species
U.S. Fish and Wildlife Service: Endangered Species Program
U.S. Fish and Wildlife Service: Threatened and Endangered Species System (TESS)
Bagheera.com: Endangered Earth
kidsplanet.org: Facts on 50 endangered species
SchoolWorld: Endangered Species Project
Colding, J., and C. Folke. 1997. The relations among threatened species, their protection, and taboos. Conservation Ecology (1): 6.